In the oil and gas industries, coiled tubing refers to metal piping used for interventions in oil and gas wells and sometimes as production tubing in depleted gas wells. Available in sizes ranging from 1 inch to 4.5 inches, coiled tubing strings are carried on reels and injected into a wellbore using a coiled tubing injector unit. A typical coiled tubing injector unit 5 is illustrated in FIG. 1. The typical unit includes a goose-neck support 3, a rotary transmission assembly, parallel drive chains 7 carrying gripping insert assemblies, skates and a hydraulic system. (The transmission assembly, gripping insert assemblies, skates and hydraulic system are not shown in detail in FIG. 1). Those skilled in the art are familiar with the components and operation of the unit 5 illustrated in FIG. 1.
The series of gripping insert assemblies carried by the chains provide the sole direct support for holding the coiled tubing in place or moving the tubing. The gripping insert assemblies are arranged in opposing pairs to secure the coiled tubing string between the injector-head chains. The hydraulic system applies pressure to the skates which in turn force the gripping insert assemblies toward each other thereby securing the coiled tubing between the gripping insert assemblies. Additionally, the hydraulic drive system drives the chains to feed the coiled tubing string into the well or pull the tubing out of the well.
During operation, wear between various components of the injector head may cause the drive chains to become elongated. Once the drive chains have become elongated by a certain amount, they are typically replaced to prevent failure. Unfortunately, it is difficult to know an exact amount by which the drive chains have elongated. Of course, the drive chains may be measured, but this requires stopping entirely any operation for which the injector head was currently being used.
Sometimes, the drive chains may be measured while they are still in the injector head. This is difficult because other parts of the injector head may be in the way, such as chain guards and other components. Removing such components is time consuming, and reassembly of the removed components after measuring may be performed improperly. The other alternative is to remove the drive chain itself from the injector head to measure its length. However, this is even more time consuming and further exacerbates problems associated with incorrect reassembly. What's more, the measurement data, once obtained, must still be used to obtain a percentage by which the drive chains have elongated. Other alternatives for use during operation are “go no go” gauges, however these may only be capable of indicating a maximum amount by which the drive chain has elongated. What is needed then is a drive chain indicator that can quickly and accurately provide a percentage chain elongation during operation of the injector head unit.
In one aspect, embodiments disclosed herein relate to an injector head unit including one or more drive chains revolving within a common plane mounted on an upper drive sprocket and a lower drive sprocket, wherein at least one of the upper and lower drive sprockets are configured to move vertically to tension the drive chains, and at least one fixed reference point proximate to at least one of the upper and lower drive sprockets, wherein relative positioning of one of the movable upper and lower drive sprockets with the fixed reference point indicates to a user an amount of elongation of the drive chains after a certain period of time.
In another aspect, embodiments disclosed herein relate to an injector head unit including one or more drive chains revolving within a common plane mounted on an upper drive sprocket and a lower drive sprocket, wherein the lower drive sprocket is configured to move vertically to tension the drive chains, one or more fixed reference points proximate to the movable lower drive sprocket, and a reference point on the lower drive sprocket configured to move relative to the one or more fixed reference points, wherein relative positioning between the lower drive sprocket reference point and the fixed reference points indicates to a user an amount of elongation of the drive chains during operation.
In yet other aspects, embodiments disclosed herein relate to a method of measuring elongation of drive chains of an injector head unit, the drive chains mounted on an upper drive sprocket and a movable lower drive sprocket and configured to revolve within a common plane, the method including providing a reference point movable with one of the drive sprockets and one or more fixed reference points proximate to the movable drive sprocket, operating the injector head unit, and determining by relative positions of the movable and fixed reference points, and without stopping operation of the injector head unit, an amount of elongation of the drive chains.